The present invention relates to manholes and particularly to manhole rings for raising and adjusting manhole and catch basin frames.
Sewer, water, electric and other underground utilities commonly require access structures to allow entry of men or equipment to perform inspection or maintenance. These structures are commonly called manholes. Manholes are typically constructed of a base, cylindrical barrel section(s), a cone section, one or more adjustment rings, and a metal frame and cover assembly. The top surface of the frame and cover assembly is generally desired to be flush with the ground surface (i.e., the surface of the road, sidewalk, etc.), both in elevation and horizontal slope. A typical method of adjusting the frame when constructing a manhole is to use one or more preformed plastic or concrete adjusting rings placed between the cone and frame to raise the top of the frame to the desired elevation. The preformed adjusting rings are generally available in nominal sizes of 2, 3, 4 or six inches in thickness. Thus, in many instances the exact elevation desired cannot be achieved using the preformed adjusting rings. A common practice is to use a combination of small cement or steel blocks and wedges to support the frame at the desired elevation and then pour or place cement into the created void, allowing it to set and provide support for the frame and cover assembly. This method of adjustment does not provide a uniform distribution or density of the cement, resulting in a material that is of potentially inadequate strength and one that may be prone to cracking and deterioration.
Another common situation requiring manhole frame adjustment is when a paved roadway is repaved or xe2x80x9coverlaidxe2x80x9d with a layer of asphalt. Existing manhole frame and cover assemblies must be raised a distance equal to the thickness of the pavement overlay to again be flush with the newly paved surface. A conventional method for raising a manhole assembly in this scenario involves removing the frame and placing a concrete or plastic adjusting ring on the existing manhole structure and then reinstalling the frame. This can be a time consuming task and generally requires at least two people to complete. Again, as previously described, meeting the exact elevation and slope can be difficult.
Other conventional methods to facilitate the positioning of the frame and cover assembly on the upper end of the manhole include arrangements of screw assemblies to raise the casting and arrangements of spacer rings placed on the existing frame as a spacer to allow the manhole cover to be reinstalled at a higher elevation. Yet another device consists of a plastic form and tool for cutting the form to proper elevation to allow the placement of concrete to form an adjustment ring on the upper end of the manhole. This process requires the manhole frame to be removed and then replaced after the concrete sets. A method and apparatus for adjusting manhole frames, which provides relatively accurate leveling of a manhole cover would be welcomed by users of manhole frames and assemblies.
The present invention provides a method and apparatus that positions a manhole frame in relation to the upper end of the manhole. The process utilizes a pressurized, flowable setting agent to lift the frame to the desired elevation and position and, when allowed to set or cure, provides a strong and permanent adjustment ring to support the frame and cover assembly. The device includes an upper and a lower ring of a rigid material, stacked one on top of the other and joined together on both their inner and outer perimeters with a flexible membrane or vertically movable containment wall. The mating surfaces of the upper and lower rings are configured to provide a cavity or channel there between. Further, an injection groove connecting the cavity or channel to an injection port on the inner surface of the apparatus facilitates the injection of the flowable setting agent into the cavity, between the upper and lower rings.
In preferred embodiments, the flexible membranes are continuous bands of a rubber or plastic material and are fastened to the upper and lower rings by adhesion or mechanical means. The bands are of sufficient width to allow the top ring to move upward a distance that is desired to be the maximum adjusting range for the device. Lateral support bands, cylindrical in shape and made of a rigid material such as HDPE or PVC are fastened by adhesion or mechanically to the inner surface of the inside flexible membrane to provide support during the pressurization process. A similar lateral support band can be fastened to the outer surface of the outside membrane to provide support during pressurization and to protect the membrane from possible abrasion from backfill material or damage during installation. The lateral support bands may be fastened to the inner and outer membranes using two congruent rigid bands, one slightly smaller in diameter than the other, one placed inside the other, with the membrane xe2x80x9csandwichedxe2x80x9d between them. The lateral support bands are of a height approximately equal to the height of the stacked, unexpanded upper and lower ring assembly.
In preferred embodiments, the setting agent includes a cementitious mixture and the inner membrane has an injection port with a hose fitting to allow the injection of the cementitious mixture into the cavity of the device. The inner membrane also has a venting port which is connected to the cavity or channel by an evacuation groove to allow air to be forced out of the cavity when replaced by the cementitious mixture or other setting agent. The venting port can be plugged after the air has been evacuated, or fitted with a fabric membrane that will allow air to escape, but will retain he setting agent.